Renal Compromise after treatment of decompensated heart failure with diuretics is not uncommon. The purpose of our study is to investigate the relationship between cystatin C and worsening renal function in this setting. Cystatin C is a biomarker produced at a constant rate by all cells that is a sensitive biomarker of renal function.Cystatin C and Plasma amino terminal proB-type natriuretic peptide (NT-proBNP) levels will be obtained at baseline and daily. Our goal is to enroll 100 subjects with an estimated 5 samples per each subject. The time course of changes in cystatin C in relation to serum creatinine levels over time will be plotted.